气候变化领域集成服务门户(CCPortal): The tungsten-182 record of kimberlites above the African superplume: Exploring links to the core-mantle boundary

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DOI	10.1016/j.epsl.2020.116473
	The tungsten-182 record of kimberlites above the African superplume: Exploring links to the core-mantle boundary
	Tappe S.; Budde G.; Stracke A.; Wilson A.; Kleine T.
发表日期	2020
ISSN	0012821X
卷号	547
英文摘要	Many volcanic hotspots are connected via ‘plume’ conduits to thermochemical structures with anomalously low seismic velocities at the core-mantle boundary. Basaltic lavas from some of these hotspots show anomalous daughter isotope abundances for the short-lived 129I-129Xe, 146Sm-142Nd, and 182Hf-182W radioactive decay systems, suggesting that their lower mantle sources contain material that dates back to Earth-forming events during the first 100 million years in solar system history. Survival of such ‘primordial’ remnants in Earth's mantle places important constraints on the evolution and inner workings of terrestrial planets. Here we report high-precision 182W/184W measurements for a large suite of kimberlite volcanic rocks from across the African tectonic plate, which for the past 250 million years has drifted over the most prominent thermochemical seismic anomaly at the core-mantle boundary. This so-called African LLSVP, or ‘large low shear-wave velocity province’, is widely suspected to store early Earth remnants and is implicated as the ultimate source of global Phanerozoic kimberlite magmatism. Our results show, however, that kimberlites from above the African LLSVP, including localities with lower mantle diamonds such as Letseng and Karowe Orapa A/K6, lack anomalous 182W signatures, with an average μ182W value of 0.0 ± 4.1 (2SD) for the 18 occurrences studied. If kimberlites are indeed sourced from the African LLSVP or superplume, then the extensive 182W evidence suggests that primordial or core-equilibrated mantle materials, which may contribute resolvable μ182W excesses or deficits, are only minor or locally concentrated components in the lowermost mantle, for example in the much smaller ‘ultra-low velocity zones’ or ULVZs. However, the lack of anomalous 182W may simply suggest that low-volume kimberlite magmas are not derived from hot lower mantle plumes. In this alternative scenario, kimberlite magmas originate from volatile-fluxed ambient convecting upper mantle domains beneath relatively thick and cold lithosphere from where previously ‘stranded’ lower mantle and transition zone diamonds can be plucked. © 2020 Elsevier B.V.
关键词	extinct radionuclides kimberlite origin LLSVP plate tectonics primordial mantle reservoirs ultradeep diamonds
英文关键词	Earth (planet); Minerals; Seismology; Shear flow; Shear waves; Structural geology; Tungsten; Volcanoes; Wave propagation; Core-mantle boundary; Isotope abundance; Radioactive decay; Seismic velocities; Shear wave velocity; Terrestrial planets; Thermo-chemical structures; Ultralow velocity zone; Volcanic rocks; African plate; basalt; core-mantle boundary; formation mechanism; igneous geochemistry; isotopic analysis; isotopic composition; kimberlite; lava; mantle source; plume; thermochemistry; tungsten; upper mantle; Africa
语种	英语
来源期刊	Earth and Planetary Science Letters
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/202926
作者单位	Deep & Early Earth Processes (DEEP) Research Group, Department of Geology, University of Johannesburg, P.O. Box 524, Auckland Park2006, South Africa; Institut für Planetologie, University of Münster, Wilhelm-Klemm-Strasse 10, Münster, 48149, Germany; The Isotoparium, Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, 91125, United States; Institut für Mineralogie, University of Münster, Corrensstrasse 24, Münster, 48149, Germany; School of Geosciences, University of the Witwatersrand, Johannesburg, 2050, South Africa
推荐引用方式 GB/T 7714	Tappe S.,Budde G.,Stracke A.,et al. The tungsten-182 record of kimberlites above the African superplume: Exploring links to the core-mantle boundary[J],2020,547.
APA	Tappe S.,Budde G.,Stracke A.,Wilson A.,&Kleine T..(2020).The tungsten-182 record of kimberlites above the African superplume: Exploring links to the core-mantle boundary.Earth and Planetary Science Letters,547.
MLA	Tappe S.,et al."The tungsten-182 record of kimberlites above the African superplume: Exploring links to the core-mantle boundary".Earth and Planetary Science Letters 547(2020).